Can't render complete images

I am trying to render my image as a PNG. I’ve imported an STL file and it looks GREAT on screen, but when I click render, I get nothing but a gray screen. It’s as if the rendered portion is only a very small section of my image. How can I get what I’m seeing to render so I can get a PNG file?

Here is what I see from the STL file:

Here is what the render looks like:

Thanks for any help!

In the outliner window is renderability turned off (camera icon)
Your object is large, select the camera and in its properties increase its clip end value
Attach or post a link to your blend file

It’s also entirely possible that you’re not looking through the camera view. The renderer will render from the active camera irrespective of whatever viewport is active. One of those unique Blender quirks.

From what’s on your screenshot looks like your object is lightyears away from blender’s usual starting point x=0, y=0, z=0. Blender’s camera by default shows objects 1000 blender units away, your’s is much further.
You have closed Outliner window, so no one is able to tell if you have camera present at all in scene. It might be deleted. Blender’s scene by default is lit by gray World light and one Pointlight which can light objects around 100 units away. If your object has no no material assigned it might be same greyish tonality and not quite well seen on render (usually not the case).

Select your object and S scale it .01 (on keyboard S .01), then Shift-S Cursor to center. After that again Shift-S, but Selection to Cursor. That will bring your object to the coordinate center and make it 100 times smaller - closer to what blender operates usually and on it’s ‘playground’.

Edit: If it was one stl file this should work; if each detail came in separate stl file you’ll probably have in addition to deal with Objects Origin first.

Ideally now you’ll be able to see Camera, Light and your object on one screen. Select camera (if it’s not in Outliner -add one) and rotate it so that it points more or less to your object. Hit “0” on numpad - if there is framed view on screen you’re looking trough Camera. Point, Render. See what happens.